function getData(endpoint) {
  return new Promise((resolve, reject) => {
    const xhr = new XMLHttpRequest()

    xhr.open("GET", endpoint)

    xhr.onreadystatechange = function () {
      if (this.readyState === 4) {
        if (this.status === 200) {
          resolve(JSON.parse(this.responseText))
        } else {
          reject('Error: Something went wrong')
        }
      }
    }

    setTimeout(() => {
      xhr.send()
    }, Math.floor(Math.random() * 3000) + 1000)
  })
}

getData("./movies.json")
  .then((movies) => {
    console.log(movies)
    return getData("./actors.json")
  })
  .then((actors) => {
    return getData("./directors.json")
  })
  .then((directors) => {
    console.log(directors)
  })
  .catch((error) => {
    console.log("出现了问题")
  })
